Rotary kiln installations



1967 E. c. P. CHRISTENSEN 3,

ROTARY KILN INSTALLATIONS Filed Aug. 5, 1965 3 Sheets-Sheet 1 RNEYS Oct. 31, 1967 E. c. P. CHRISTENSEN ROTARY KILN INSTALLATIONS Filed Aug. 5, 1965 E'Sheets-Sheet 2 42k ZZQ Em ZZAMSM 3 M ATTORNEYS Oct. 31, 1967 E. c. P. CHRISTENSEN 3,350,077

ROTARY KILN INSTALLATIONS Filed Aug. 5, 1965 I 3 Sheets-Sheet 3 INVENTOR ATTORNEYS United States Patent 3,350,077 ROTARY KILN INSTALLATIONS Erik Christian Parmo Christensen, Copenhagen-Valby, Denmark, assignor to F. L. Smidth & C0., New York, N .Y., a corporation of Delaware Filed Aug. 5, 1965, Ser. No. 477,555 11 Claims. (Cl. 263-32) ABSTRACT OF THE DISCLOSURE An installation basically including a rotary kiln and a grate cooler for receiving material from the kiln and cooling material by passing air through it is provided with some improvements. A plurality of passageways extending through the kiln shell in a circumferential series with outer end openings through which material is discharged into a casing above the grate and directly onto the grate in several flows transversely across the grate as the openings successively travel across the bottom of the kiln as the kiln rotates through the lower half of a cycle; by this means material which is of substantially uniform thickness from one side of the grate to the other is deposited.

This invention relates to installations which are employed for the production of cement clinker, burned lime, sintered ores, and like materials and include a rotary kiln and a grate cooler receiving material from the kiln and cooling the material by passing air through it. More particularly, the invention is concerned with a novel installation of the type referred to, which provides more satisfactory cooling of the material than is obtainable in prior similar installations. The improved effects afforded by the installation of the invention result from more even distribution of the burned material upon the grate and avoidance of clogging of the grate 'by dust particles and are achieved by novel features of the kiln and cooler.

In installations including a rotary kiln and a grate cooler as heretofore constructed, the kiln is mounted at a low angle to the horizontal with the grate below its lower end and, as the kiln rotates, the burned material is discharged in a continuous stream from a short are of the kiln slightly offset in the direction of rotation from the lowest point of the kiln outlet end. The falling material collects on the grate in a pile having its highest point at the bottom of the stream so that, as the material is carried away, the bed, through which the cooling air passes, is much thicker at its middle than at its sides. As a result, the major proportion of the cooling air passes through the thinner parts of the bed and the cooling is not uniform.

lAnother objectionable feature of rotary kiln-grate cooler installations as heretofore constructed is that the air for cooling, which is customarily led back to the kiln for use in combustion, travels in contact with the material being discharged from the kiln. The material issuing from the kiln contains a varying proportion of fine particles together with larger lumps and such dust tends to clog the grate and reduce the permeability of the material to air. In addition, the cooling air entrains dust on the grate and dust falling from the kiln toward the grate and carries the entrained particles back into the kiln.

The installation of the invention overcomes the objectionable features of prior similar installations and provides more uniform cooling of the material and avoidance of clogging of the grate by dust and of return of dust particles to the kiln. In the new installation, the kiln is provided with a plurality of passageways through the kiln shell in a circumferential series and, as the kiln rotates, the. burned material is discharged through the passageways in succession as the openings to the passageways travel across the bottom of the kiln. Each stream of material issuing through a passageway moves transversely of the grate and, as a result, the material forms a bed on the grate, which is of approximately uniform thickness across the grate. The material issuing through the passageways enters a casing containing the grate and so constructed as to provide separate passageways for the discharging material and for the air traveling from the grate into the kiln. In order to prevent air which has passed through the grate, from flowing to the kiln through the passageway for the material, means are provided for maintaining an air pressure in the material passageway which is substantially equal to the pressure within the kiln at the entrances to the discharge passageways. The means for maintaining the pressure equality may also be employed for diverting part of the air stream from the grate through the streams of material falling from the kiln to entrain dust therefrom and the dust may be separated from the air stream outside the casing and the air stream then returned for cooling purposes.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which FIG. 1 is a longitudinal vertical sectional view on the line 1-1 of FIG. 2 of parts of a typical kiln-cooler installation as heretofore constructed;

FIG. 2 is a transverse vertical sectional view on the line 22 of FIG. 1;

FIG. 3 is a view similar to FIG. 1 of a kiln-cooler installation constructed in accordance with the invention;

FIG. 4 is a sectional view on the line 44 of FIG. 3;

FIGS. 5 and -6 are partial sectional views similar to FIGS. 3 and 4, respectively, of a modified installation;

FIGS. 7 and 8 are sectional views similar to FIGS. 3 and 4 of a second modified installation; and

FIGS. 9 and 10 are views similar to FIGS. 3 and 4 of a third modified installation.

The conventional kiln-cooler installation shown in FIGS. 1 and 2 includes a rotary kiln 11 provided with a lining 12 and mounted at a slight angle to the horizontal. At its lower discharge end 13, the kiln shell includes an internal radial flange 14 forming a dam ring and the lining extends to the inner edge of the ring so as to cause an accumulation of the burned material 15. As the kiln rotates, the material is discharged in a continuous stream 16 over the edge of a small arc of the dam ring which is offset from the lowest point of the discharge end of the kiln (FIG. 2).

The lower end of the kiln extends into and is sealed in an opening in a lined casing 17 through which the fuel pipe 18 extends to projectinto the kiln through its open discharge end. The casing 17 may be considered as part of a cooler which contains a grate 19 which may either be of the moving type or else include reciprocating members which advance the material to the left as viewed in FIG. 1. Beyond the end of the grate, the casing is provided with an inclined screen 20 leading to a spout 21 for discharge of the oversize pieces sliding from the screen, while the material which passes through the screen, leaves the casing through a shaft 22. Air under pressure enters the space 23 within the casing below the grate through a pipe 24 and the air which has passed through the grate and the material thereon travels upward through the casing and enters the kiln through its open discharge end. The flow of air into the kiln is regulated by. a vent pipe 25 leading from the top of the casing and containing a butterfly valve 26. Adjustment of the valve determines the proportions of the cooling air which will enter the kiln and escape to the atmosphere through the pipe 25 and the pipe is disposed at the downstream end of the grate to reduce the heat loss as a result of air leaving the cooler past the valve 26.

As will be apparent from FIG. 2, the stream of burned material discharging from the rotating kiln collects on the grate 19 to form a bed 27 which is much higher at the middle than at the edges. The thickness of the bed depends on the output of the kiln and the conveying speed of the grate but the distribution remains the same whatever the maximum thickness of the bed may be. Because of the greater resistance to the passage of air through the middle of the bed, the material at the sides in subjected to the greatest cooling effect and the cooling of the material is non-uniform because of the variation in thickness of the bed from one edge to the other as described.

In the installation shown in FIGS. 3 and 4, the rotary kiln 28 is provided at its lower end with a radial flange 29 forming a dam ring and the end of the kiln is open for admission of air. Upward from its open end, the kiln is provided with a plurality of passageways 30 formed through the kiln shell and lining in a circumferential series. A pipe 31 is mounted on the outer wall of the kiln shell to extend radially and form part of each passageway and the pipes 31 widen in an outward direction. The spaces between the pipes are sealed by plates 32 connected to adjacent pipes and the outer ends of the pipes and plates are sealed to a stationary annular casing 33.

The lower end of the kiln extends into a casing 34 of a cooler and the casing contains a grate 35 and upper and lower horizontal walls 36, 37 connected by side walls 38. The walls 36, 37, 38 serve as partition means to define a shaft 39 leading downward from the lower end of the casing 32 and serving as a passageway for the descent to the grate of material being discharged from the kiln through the passageways 30, 31. The partition means also define a passageway 40 leading from the top of the casing to the open discharge end of the kiln. In order to cool the side walls 38, air or water may be supplied by a pipe 41 for circulation through the space defined by the Walls 36, 37, and 38.

The space beneath the grate within the casing 34 is subdivided into a chamber 42 lying below the bottom end of the passageway 39 and the partition wall 36 and a chamber 43 lying beneath the remainder of the grate. Air is supplied to chambers 42 and 43 by respective fans 44, 45 and the casing is provided with a vent pipe 46 containing a butterfly valve 47 for regulation of relative amounts of air permitted to escape to the atmosphere and caused to enter the kiln through its open lower end.

A pipe 48 having an intake as wide as the passageway 39 leads from the passageway at about its mid-point to cyclone separators 49, 50 connected in parallel and having their air outlets connected by pipes 51, 52 to the intake of a fan 53 having its outlet connected by pipes 54, 55, 56 to the intakes of the fans 44, 45. The separators 49, 50 have outlets for separated solids at their lower ends and the outlets lead to the casing of a screw conveyor 57 of the type which is sealed to prevent air from being sucked through it. The pipe 48 leading from the passageway 39 to the separators has a branch 58 containing a butterfly valve 59 and the pipe 52 may be provided with a branch 60 containing a butterfly valve 61. By adjustment of the valve 59, the air flowing to the separators may be tempered by the addition of cold atmospheric air and the valve 61 may similarly be adjusted to permit the entrance of cold air into the pipe 52 to mingle with the air passing therethrough. By adjusting the speed of fans 44, 45, and 53, and the chimney fan with which the kiln is provided, the extent of cooling of the material on the grate above the chamber 42 can be adjusted and the pressure within the passageway 39 may also be adjusted so as to be substantially the same as that within the kiln adjacent the inner ends 30 of the passageways 31. When this equality of pressure is maintained, there is no tendency for air to travel upward through the passageway 39 and into the kiln countercurrent to the discharging material.

The separated solids entering the casing of conveyor 57 from the separators may be added to the material leaving the cooler through the spout 62 at the end of the grate 35, as indicated by the dotted line 63. However, if the separated dust is not suitable for use with the cooled material discharged from the end of the grate, it may be rejected.

In the operation of the installation shown in FIGS. 3 and 4 in the manufacture of cement clinker, for example, the clinker is discharged from the kiln through the passageways 31 as the passageway openings 30 successively travel across the bottom of the kiln, and the discharging material is deposited on the grate to form a bed 64, which is of substantially uniform thickness from one side of the grate to the other. Because of the uniformity of thickness of the bed, more uniform cooling of the material is obtained and the provision of separate passageways 39, 40 for the material leaving the kiln and the air being conducted to the kiln, respectively, reduces the return of dust to the kiln. Dust is also removed from the stream of material traveling through the passageway 39 by the withdrawal of air through the pipe 48 leading from the passageway, so that less dust is deposited on the grate and the likelihood of clogging is reduced.

The kiln 28 in FIG. 3 is provided with four passageways 31 disposed equiangularly about the kiln. If desired, the kiln may have more passageway, for example 8, but it has been found that the use of the smaller number of passageways results in a more even distribution of material on the grate.

The installation shown in FIGS. 5 and 6 differs from that shown in FIGS. 3 and 4 only in the respect that the casing 32 is replaced by a cylindrical wall 65 supported by a plate 66 attached to the casing 67 of the cooler. The kiln is provided with a circumferential series of passageways 68 for discharge of the burned material and the wall 65 closes the ends of the passageways except those lying above the passageway 69 which corresponds to the passageway 39.

In the installation shown in FIGS. 7 and 8, the kiln 70 has passageways 71 for the discharge of material which are formed by pipes leading only through the lining 72 and the shell 73 of the kiln. The lower end of the kiln is closed by a stationary plate 74, through which the burner tube 75 projects and the casing 76 of the cooler extends up the kiln beyond the outer ends of the passage ways 71. The interior of the casing thus forms an extension of a passageway 77 for material being discharged from the kiln through the outlet passageways 71 but is separated from the passageway 77 by partitions 78, 79 within the casing. Air for cooling is supplied under pressure to the chambers 80a, 80b beneath the grate and the air passes through the grate 81 and the bed of material 82 thereon. The air then travels upward through the passageway 83 and enters the kiln through the passageways 71 through which discharge of material is not taking place. In order to prevent entry of air into the kiln through its lower end, a seal 84 is provided between the plate 74 and the darn ring 85 at the end of the kiln.

The installations shown in FIGS. 5, 6, and 7, 8 include vent pipes for discharging a part of the heated cooling air into the atmosphere and may include cyclones and associated features, as shown in FIGS. 3 and 4, if desired. In the two modified installations, the cooler casing includes internal partition means providing the separate passageways for material being discharged from the kiln and heated cooling air 'being supplied to the kiln.

In the installation shown in FIGS. 9 and 10, the shell of the kiln 86 is provided with an internal flange 87 at its lower end forming a dam ring and the opening through the dam ring 87 is closed by a stationary plate 88 sealed to the dam ring. An air pipe 89 leads from the top of the cooler casing 90 to an opening through the plate 88 and the burner pipe 91 extends through another opening in the plate.

Passageways 92 for discharge of material from the kiln extend from the inner surface of the kiln lining 93 through the dam ring and diverge outwardly from the kiln axis. The material discharged through the passageways drops down through an upright shaft 94 forming part of casing 90 to fall upon the grate 95 within the casing. The shaft is provided with an air pipe 96 which serves the same purpose as the pipe 48 in the installation of FIGS. 3 and 4 and leads to cyclones, fans, etc., by which air may be withdrawn from the shaft to entrain and remove dust from the falling material and the air pressure within the shaft may be maintained to prevent a back-flow of air up the shaft and into the kiln.

I claim:

1. A kiln installation which comprises a rotary kiln, a casing at the discharge end of the kiln in communication with the interior of the kiln, a transversely horizontal grate defining a substantially horizontal plane inside the casing in position to receive material discharged from the kiln, means for depositing burned material from the kiln upon the grate to form a bed of approximately uniform thickness across the grate, including a plurality of passageways through the kiln shell in a circumferential series with outer end openings through which material is discharged into the casing above the grate and directly onto the grate in several flows transversely across the grate as the openings successively travel across the bottom of the kiln as the kiln rotates through the lower half of a cycle and thereby depositing material from one side of the grate to the other, means for advancing the bed, and means for passing air through the grate from beneath to cool the material and heat the air.

2. The installation of claim 1, which includes means for conducting heated air from the grate into the kiln out of contact with material during its discharge from the kiln and onto the grate.

3. The installation of claim 2, in which the kiln has a closure at its discharge end and a pipe conducts air from the casing above the grate to an opening in the kiln end closure to provide secondary combustion air in the kiln.

4. The installation of claim 2, in which the casing is provided with partition means defining separate passageways through which heated air is connected to the kiln and burned material from the kiln is conducted to the grate.

5. The installation of claim 4, in which the discharge end of the kiln is open and the air passageway in the casing leads to the open kiln end.

6. The installation of claim 4, in which the discharge end of the kiln is closed and the air passageway in the casing leads to the passageways through the upper part of the kiln shell.

7. The installation of claim 4, which includes means for maintaining air pressure in the passageway for the burned material substantially equal to the air pressure inside the kiln at the inner ends of the passageways through the kiln shell.

8. The installation of claim 7, in which the air pressure maintaining means includes a pipe connected to the passageway for burned material, a fan for drawing air through the pipe and discharging it into the casing below the grate, and means for separating fine particles from the air passing through the pipe to the fan.

9. The installation of claim 1, in which the passageways through the kiln shell include pipes attached to the kiln around openings through the kiln shell and extending outwardly from the shell.

10. The installation of claim 1, in which the kiln shell includes a dam ring, the ring is protected by a lining, and the passageways extend from the interior of the kiln through the lining and ring.

11. The installation of claim 10, in which the discharge end of the kiln has a closure, and an air pipe leads from the casing above the grate to an opening in the closure.

References Cited UNITED STATES PATENTS 1,739,383 12/1929 Bauchere et a1. 26332 2,019,179 10/1935 Fasting 26-332 2,859,955 11/1958 Petersen 26332 3,042,388 7/1962 Sainty 263-32 FOREIGN PATENTS 921,256 12/ 1954 Germany. 508,500 6/1939 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner. JOHN J. CAMBY, Examiner. 

1. A KILN INSTALLATION WHICH COMPRISES A ROTARY KILN, A CASING AT THE DISCHARGE END OF THE KILN IN COMMUNICATION WITH THE INTERIOR OF THE KILN, A TRANSVERSELY HORIZONTAL GRATE DEFINING A SUBSTANTIALLY HORIZONTAL PLANE INSIDE THE CASING IN POSITION TO RECEIVE MATERIAL DISCHARGED FROM THE KILN, MEANS FOR DEPOSITING BURNED MATERIAL FROM THE KILN UPON THE GRATE TO FORM A BED OF APPROXIMATELY UNIFORM THICKNESS ACROSS THE GRATE, INCLUDING A PLURALITY OF PASSAGEWAYS THROUGH THE KILN SHELL IN A CIRCUMFERENTIAL SERIES WITH OUTER AND END OPENINGS THROUGH WHICH MATERIAL IS DISCHARGED INTO THE CASING ABOVE THE GRATE AND DIRECTLY ONTO THE GRATE IN SEVERAL FLOWS TRANSVERSELY ACROSS THE GRATE AS THE OPENINGS SUCCESSIVELY TRAVEL ACROSS THE BOTTOM OF THE KILN AS THE KILN ROTATES THROUGH THE LOWER HALF OF A CYCLE AND THEREBY DEPOSITING MATERIAL FROM ONE SIDE OF THE GRATE TO THE OTHER, MEANS FOR ADVANCING THE BED, AND MEANS FOR PASSING AIR THROUGH THE GATE FROM BENEATH TO COOL THE MATERIAL AND HEAT THE AIR. 